During installation of pipelines they can often be dented or buckled as a result of construction activity, such as during the backfilling the ditch in which they are laid and so forth. After pipelines have been installed they still are subject to becoming damaged due to the effect of temperature changes causing stretching and buckling, freezing and thawing of the earth, shifting in the earth's structure, damage from other construction activities, and so forth. In addition, debris can gather in certain areas in a pipeline forming an obstruction to the flow of fluid therethrough. For these and other reasons, a technique which has been employed in the pipeline industry to determine the character of the internal pipeline wall is to pass a caliper pig through the pipeline. The caliper pig was invented by Burton VerNooy, patentee of U.S. Pat. No. 3,755,906 entitled "Pipeline Pig". The pipeline pig of the VerNooy invention includes a body assembly with spaced apart cups affixed to the body. The cups form the dual function of supporting the body in the pipeline and at least one of the cups interfere with the fluid flow through the pipeline so that the pig is carried along by the fluid flow. Attached to the body are a plurality of arms which extend out to engage the interior of the rearward cup. Coupling members extend from the arms to an integrator plate which is attached to an axially positionable central shaft. Within the pig body is an instrument package providing a moving chart. A pen stylus is affixed to the inner end of the shaft.
As the pipeline pig of the VerNooy patent passes through a pipeline and encounters a deflection of the inner pipeline wall, the cup is deformed and thereby one or more of the finger mechanisms is deflected. This deflection is transmitted to the integrator plate which causes the axial shaft to be displaced. The shaft displacement is indicated on the chart. By means of an odometer system the chart is moved in proportion to the travel of the pig through the pipeline so that after the chart has been recovered following a complete run of a pig, the extent of and the location of a deviation in the pipeline wall is indicated.
While the pipeline pig of U.S. Pat. No. 3,755,908 works exceedingly well and has proven to be a great boom to the operators of pipelines in the United States and many parts of the world, nevertheless, it has some deficiencies. A primary deficiency of the pipeline pig as disclosed in U.S. Pat. No. 3,755,908 is that when an anomoly in the interior wall of a pipeline is detected it is recorded in the same manner on the chart regardless of the axial orientation of the anomoly. For instance, if an interior protrusion occurs in a pipeline it will be indicated and the depth of the protrusion and its location along the length of the pipeline will be indicated; however, the axial orientation is not indicated, that is, whether the indentation is at the top, bottom or sides of the pipeline is not known to the operator. Further, the moving paper chart must move at a relatively slow rate to permit a pipeline pig to travel several miles within a pipeline, therefore, the characteristics of anomolies which are detected can not be easily determined from the paper chart.
The present invention overcomes these problems associated with the presently known caliper pigs represented by U.S. Pat. No. 3,755,908. The invention provides an improved caliper pig, which, among other advantages, produces a rotationally oriented signal detection system so that the record provides not only the location and depth of a protrusion, as an example, but also the axial orientation thereof relative to the vertical. In addition, means is provided for greatly improving the quality of the records so that more information is provided as to the size and shape of any anomoly detected in the interior pipeline wall.
To accomplish these goals the present invention includes a pig body assembly having a longitudinal axis. Means is provided in the form of spaced apart cups of resilient material for supporting the pig body within the pipeline. At least one of the cups is impervious to fluid flow, that is, impedes fluid flow so that the pig is moved through the pipeline interior by the flow of fluid. Contained within the body assembly is a closed instrument package and batteries.
Affixed to the pig body assembly in conjunction with the rearward most resilient cup is an integrator plate. Extending from the integrator body assembly are a plurality of spaced apart fingers, each hinged at its inner end to the pig body assembly. The outer ends engaging the cup to thereby deflect in conformity with the deflection of the cup. The movement of the fingers are each individually conveyed to the integrator plate by means of coupling members extending from the fingers to the periphery of the integrator plate.
At least three shafts are connected to the integrator plate, the axis of each of the shafts being parallel to the longitudinal axis of the pig body assembly. In the preferred arrangement one of the shafts is a central shaft, the axis of which is coincident with the body longitudinal axis with the other two shafts being spaced from the central shaft and spaced from each other, such as 120.degree. apart, as an example.
Affixed to the inner end of each of the shafts is an electrical transducer, that is, an element which transforms the axial displacement of each of the shafts into an electrical signal. This is accomplished by means of a rotary potentiometer each having a short shaft extending therefrom with a crank arm extending from it. Each of the shafts connected to the integrator plate are provided with a follower which engages a potentiometer crank arm. As the integrator plate is pivoted in response to changes in the internal configuration of a pipeline wall the displacement of the shafts are transformed into electrical signals.
An odometer system is employed to provide a signal in response to the movement of the pig through the pipeline. The odometer system preferably employs two odometer wheels each of which provides an electrical signal indicating its rotation, the odometer wheels being resiliently biased against the interior of the pipeline. The signals are fed to an instrument package which also receives the signals from the transducers connected to the shafts extending from the integrator plate. In addition, a gravitationally sensitive indicator is carried by the body assembly and provides electrical signals indicating the orientation of the pig body relative to the vertical. The orientation signals when coordinated with the signals produced by the three shafts extending from the integrator plate provide means of indicating the position relative to the vertical of an internal deflection of the pipeline wall while the signals provided by the odometer system identifies the position of the internal deflection relative to the length of the pipeline.
An alternate embodiment of the invention provides means for detecting and recording changes in the direction of a pipeline, such as curves, bends, dips and rises. For this purpose three or more odometer wheels are secured to the pig body assembly arranged in a common plane perpendicular to the body assembly longitudinal axis and spaced in equal angular relationship. When three odometer wheels are employed they are spaced 120.degree. apart.
Each odometer wheel includes a means of producing an electrical signal indicative of the rotation of the wheel, such as one pulse per revolution. These signals are fed to the electronic package where the signals are stored along with the other signals, such as those from the orientation card. Upon completion of a run of the pig the recorded signals may be employed in a computer, utilizing an appropriate program, to provide a record of the changes in direction of the pipeline, which changes can be coordinated with the detected changes in orientation of the pig relative to the vertical so that the final record will reveal curves to the left or right or inclines or decline of the pipeline. Such detected changes in direction of a pipeline when coordinated with recorded distance measuring odometer signals help to more precisely identify the location of a detected deviation in the pipeline wall so that the operator will know more precisely where to uncover the pipeline for external visual inspection of a problem area.
More details of the invention will be set forth in the attached description and claims, including the attached drawings.